The interaction of nuclear and organelle genomes will be examined with respect to the inheritance and functional properties of chloroplast and cytoplasmic ribosomal RNA and proteins. Biochemical and genetic analyses using several species of Nicotiana and their F1 hybrids will be performed in order to decide whether chloroplast DNA carries genes which uniquely code for any of the proteins or the RNA nucleotide sequences of chloroplast ribosomes and to determine if any of the genes involved are also shared with those coding for cytoplasmic ribosomal macromolecules. Gel electrophoresis studies of differences and identities in protein composition of chloroplast and cytoplasmic ribosomal subunits will be completed. From analysis of reciprocal hybrids between various Nicotiana species, it will be determined if interspecific differences in chloroplast ribosomes exhibit a Mendelian or cytoplasmic mode of inheritance. We will assess whether ribosomal protein and RNA differences between species are associated with stability or antibiotic sensitivity of intact ribosomes or their subunits. BIBLIOGRAPHIC REFERENCES: D.P. Bourque, A. Hagiladi, and S.G. Wildman. Experimental test of a TMV replication model. Attempts to identify molecular precursors of TMV-RNA molecule. Virology 63:135-146, (1975). D.P. Borque, P.N. McMillan, W.J. Clingenpeel, and A.W. Naylor. Ultrastructural effects of water stress on chloroplast development of jack bean. Plant Physiology 56:160-163, (1975).